Only if you are cherry-picking small blocks. Forest Hill is a mixed-use area, with much housing that is not single family dwelling. It also has access to good public transit. This is also an area specifically built to house the wealthy, which require the larger structures and lots. Good urban planning will set aside some areas for this purpose, as a city needs to attract this demographic if it is to accommodate a healthy mixed-income population. The difference is...you have to pay for that luxury. I'm sure market values and taxes on a Forest Hill property is far more than your average suburban one.
Again..they are only similar on a cherry-picking micro scale. And it isn't about density for the sake of density. Density has value if it cultivates and supports positive attributes. Brazilian slums have higher densities...but whoop dee doo.
Average urban property values in Toronto are going to be higher. But older pre-war nabes in Toronto experience gentrification, whereas this trend is not very common in the suburbs. In fact. I think the opposite may be true.
I don't think I'm cherry picking. If you take the average residential block in a neighbourhood built in the last 2-3 decades, the densities are comparable to an average residential block in 1920s vintage streetcar suburbs.
So then the question is why they function differently and why they're less dense at a larger scale. A big part of the difference is the non-residential stuff, especially employment lands, and to a lesser degree, more schools with big schoolyards (also parking lots), often more ravines (while Old Toronto buried a ton)... although more stormwater ponds, and low density shopping centres. And less apartment buildings too, although it's not that the suburbs are all detached SFH either.
And yes, a house in Forest Hill is more expensive. A comparably sized house on a comparably sized lot in the suburbs, like say on Dolomite Court in Vaughan, might cost "only" around 2 million. In the city blocks of Forest Hill I used in my example, it would probably be around $5 million. By the way, the reason I used the Forest Hill example is to show how the least urban part of pre-WWII Toronto stacked up against the suburbs. Obviously "least" is not equal to "representative". But yes, that part of Forest Hill is not hugely different from the suburbs. Driving commute mode share is about the same as the post-WWII parts of the GTA. As for being mixed use/mixed housing type, those particular city blocks are about a 10 minute walk from the closest multifamily, and a 15 minute walk from the closest retail, which is not really different from the typical suburb. They do have a subway nearby, in fact, two subways, plus a streetcar and busy bus routes, but that has nothing to do with that low density part of Forest Hill and everything to do with how those lines fit into the regional transit network, and with the higher density nodes elsewhere in the area.
By the way, I think a big factor in how the suburbs function is location. The population density of newer neighbourhoods is pretty close to Toronto's streetcar suburbs. If you were to increase the population density to make up for the additional space dedicated to ravines, parks and low density shopping centres, I don't think the outer suburbs would function radically differently. That doesn't mean density is a bad measure, but maybe there are other ways of measuring density to get a full picture.
What I would propose is combining the retail/job and residential density at the walking distance scale, and also the job and residential density at the transit commute scale (5-10km). Although many here might be tempted to say that the difference between pre-WWII and post-WWII neighbourhoods is the job/retail density, at the walking scale, both pre-WWII and post-WWII neighbourhoods typically have some local retail and schools, and often not that much else. The degree of mixed use at the walking scale is not as huge as you'd expect. I thought I'd check out SW suburban Brampton, and compare it to the streetcar suburb type neighbourhoods in Toronto's east end. For Brampton, I got 2.78 workers per job, and for the East End, 2.4 workers per job. The difference is pretty small, if not for Toronto East General Hospital, they'd be even. It's not some tiny cherry picked area either, both have about 30,000 workers (so 60-90k residents). And it's not that the east end has the jobs more evenly distributed, in fact, they're less evenly distributed. The thing is, both are pseudo-bedroom communities*.
So then what is the difference? I think Downtown Toronto is the big one. The East End is within transit commuting distance of Downtown, which is probably why it has the bones of a pseudo-bedroom community. This means that you achieve a balance of jobs and workers within transit commuting distance, and that the jobs+residents density within transit commuting distance is high (Downtown is very dense). How about the suburbs? In many cases, you do not achieve a balance of jobs within 5-10km. Even if you do, the density at the transit scale is likely lower than at the walking scale, while for streetcar suburbs it's almost the opposite. For the streetcar suburbs, the transit scale density is boosted by downtown, while for new developments, it's brought down by older post-WWII suburbs and low density industrial employment zones.
By the way, I don't think the problems of Brazilian slums are necessarily caused by density, and despite their problems, I suspect they have a pretty strong sense of community and are pretty pedestrian oriented, and that their density does have a role in that.
*Pseudo bedroom community as in the main thing that exists aside from homes is parks, schools, and local oriented retail, with a lack of major job centres (office, industrial, institutional) or regional/destination retail.
